Check baggage regulations.
Make sure that you check the baggage regulations for your specific airlines. These regulations can change and differ from airline to airline, or even destination to destination with the same airline, so it’s important you check your airline’s regulations to avoid any nasty surprises at the check-in desk.
Remember that it’s not only your checked in baggage that has weight limits but also your hand held luggage. Recently I’ve seen more cases of check in desks weighing all bags – cabin and checked in – to ensure that people aren’t trying to cheat the system by putting the over-limit weight into their cabin luggage.
If you think you will be over the limit or be checking in baggage which isn’t included in the flight fare, it is usually cheaper to book this online before heading to the airport. While traveling with budget airline Jetstar in Australia, we had pre-booked our baggage knowing that we would need an additional bag. At the airport we saw a family having to pay for an additional bag because they had tried to cheat the system (as I explained above) and the price difference between what we had paid online and what they needed to pay at the desk was shocking (at least 3 times more).